In accordance to the 16 June 2010 issue of ScienceDaily, a study conducted by the University of Maryland has discovered that crayfish are able to make amazingly complex, cost-benefit calculations, thus opening the door to a novel field of study that may assist in unveiling the cellular brain activity that is involved in human decision making.
Based on the conclusions of the Maryland psychologists, the crayfish makes an outstanding, practical model to identify the particular neural circuitry as well as neurochemistry of decision making. They are of view that their research is the very first to separate individual crayfish neurons that are involved in value-based decisions. At this time, there is no direct method to perform this with the brain of a human being. The study has been published in the Proceedings of the Royal Society B.
Jens Herberholz, psychologist at the University of Maryland, as well as the leading author of the study, explains that for the time being it is simply impossible to match individual neurons to the processes of decision making that occur in the human mind.
He further advances that history has demonstrated that discoveries made in the invertebrate nervous systems usually translate to organisms that are more complex. It is most improbable to be precisely the same; however, it can nevertheless enlighten our understanding of the human brain. The underlying organization of neurons and the fundamental neurochemistry are alike, comprising of dopamine and serotonin, for instance.
Additionally, according to Herberholz, his laboratory’s work may provide information to current studies that are being carried out in relation to primates and rodents. He states that the combination of findings from varied animal models is the single practical way in order to be able to work out the intricacies of human decision making at the level of cells.
The experiments that were done involved providing the crayfish harsh decisions- choosing between searching for their next meal and becoming a meal for an evident predator instead. According to Herberholz, while deciding on which course of action t adopt, the crayfish cautiously weighed the risk of being attacked against the anticipated reward.
By making use of a non-invasive approach that permitted the crustaceans to move freely, the researchers provided young Louisiana Red Swamp crayfish a threat and a reward simultaneously; in front lay the scent of a meal, however, the apparent approach of a predator too.
In various cases, the predator, which was in fact a shadow, seemed to be moving quickly, in other cases it moved rather slowly. To increase the ante, the researchers also differentiated the intensity of the odor of the meal.
What would be the reaction of the animals? Did the probability of becoming the meal of the predator outweigh their wish to feed themselves? Should they “freeze” – that is, playing dead, in the hope that their predator would pass by, while the crayfish stayed close to its food – or distance itself both from the food and the predator?
In order to escape quickly, the crayfish flip their tails and start swimming backwards, an action that is preceded by an intense and measurable electric neural impulse. The tanks that were specially designed could pick up and record these electrical signals in a non-invasive manner. This permitted the researchers to make out the activation patterns of particular neurons throughout the process of decision making.
Even though tail-flipping is considered to be a very efficient escape strategy against natural predators, it augments significant distance between an animal and its subsequent meal. The crayfish went through vital decision making in a matter of milliseconds. When they were faced with very swift shadows, they were considerably more prone to freeze instead of tail-flipping away.
The researchers reached the conclusion that there is in fact little motivation for retreat when the predator seems to be moving too quickly for escape, and the crayfish would lose its own chance to eat. This also holds true when the odor of the food was the strongest, increasing the benefit of remaining close to the anticipated reward. The stimulus of a strong predator was however able to outweigh an attractive food signal and crayfish took the decision to flip away under these circumstances.
The researchers write that their results point out that when the relevant values of tail-flipping and freezing alter, the crayfish regulate their choices accordingly, hence conserving adaptive action selection. They have demonstrated that crayfish, same as organism of greater complexity, integrate diverse sensory stimuli that exist in their surrounding, and they choose a behavioral output based on current values for every choice.
The subsequent step is to make out the particular neurochemical and cellular mechanisms that are involved in the decisions of crayfish, which is more practical in an animal with lesser and accessible neurons, said Herberholz. That study is actually underway. The University of Maryland’s Division of Research and National Science Foundation have taken the responsibility to fund the research of Herberholz.
Source: Science Daily
Sat, Jun 19, 2010
Bioscience, Gerontology, Lifestyle